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Vortex-induced Vibrations And Lock-in Phenomenon Of Bellows Structure Subjected To Fluid Flow


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M. Watanabe & M. Oyama


This paper deals with an experimental study on vortex-induced vibrations of bellows structures subjected to fluid flow. In the experiments, the bellows structure consists of flexible convolutions, and is subjected to fluid flow in a water channel. The vibration strains of the flexible convolutions are measured with increasing flow velocity. The vortex-induced responses are examined with changing the convolution pitch and number of the flexible convolutions. Moreover, the vortex shedding coupled with the vibrations of the convolutions is visualized. As a result, it is clarified that the vortex-induced vibration and lock-in phenomenon occur to the flexible bellows structures with large amplitude. The boundary of the lock-in region and Strouhal number are clarified, and detailed excitation mechanism of the vortex-induced vibration and lock-in phenomenon due to the vortex shedding is presented. Keywords: vortex-induced vibration, vortex shedding, bellows structure, lock-in phenomenon, Strouhal number. 1 Introduction Flexible bellows are used widely in many industrial applications as expansion joints conveying fluid in piping and engine systems. Unfortunately, flexibility of the bellows makes them susceptible to vibration and, in particular, flow-induced vibration resulting from internal flow across the tips of the bellows convolutions. Up to this time, some research has been conducted on flow-induced vibrations of the bellows due to internal fluid flow. Gerlach [1,2] examined the detailed


vortex-induced vibration, vortex shedding, bellows structure, lock-inphenomenon, Strouhal number.